I use a separate policy for the SQL full and the SQL incremental backups. However, You can add additional clients to the policies as long as you use the same batch file names.
Policy_SQL__FULL
File_list = batch.full
Client list = clientA, clientB, clientC
Policy_SQL_INCR
File_list = batch.incr
Client list = clientA, clientB, clientC
Policy_SQL_TRAN
FILE+LIST = batch.tran
Client list = clientA, clientB, clientC
That helps to cut down on the number of policies